Down to earth with earthworms
Earthworm dissection, Pre-AP Biology, Rachel Lu
Objectives
In this investigation, we will be observing the external and internal structures of an earthworm. The systems that are identified in this investigations are the circulatory and the digestive system, but in this case we will be focusing on the digestive system.
Lumbricus Terrestris
The earthworm is commonly known to scientists as Lumbricus Terrestris. Despite the size, these earthworms have a complex digestive system. The food passes into two small organs, where it is grounded up and digested. After that it is moved to the small intestine.
To Eat, or to be Eaten
The earthworm eats many things, but its main diet is eating organic material such as plants insect parts and bacteria. Many organisms prey on the earthworm, which include numerous animals like birds, rats, and toads.
Where do you belong?
The classical earthworm is a decomposer, because it takes dead or rotting things and digests it. Later it will then recycle this nutrients back into the environment in the form of nutritious soil.
The Giant Earthworm
Location Location Location
Although the earthworms are native to Europe, they are now found all throughout the world. Although several species live in various layers of the soil, they can also be found in other places such as a rotting log or along bodies of water. Earthworms have to generally remain at a close distance to its food supply in order to survive, and the environment has to be moist because the earthworm breaths through its skin. Earthworms are also very sensitive to light and they prefer a moist and warm living condition, rather than overexposure to light and dryness.
Classification
The classification of the earthworm
Cladogram
The diagram shows where the earthworm come in, and which organisms it is similar to and vice-versa.
Adaptions
The dorsal side of an earthworm is darker than the ventral side, therefore it blends into the surroundings. This makes it harder for the prey to find the worm, making it a useful adaptation. Also the worms streamline body allows it to borrow in the dirt effortlessly and its body is uniquely adapted to the underground conditions. Earthworm are born blind and deaf, so it relies on the vibrations in the ground to know if predators are near.
Internal Organs
pharynx, heart, seminal vesicles, seminal receptacles, crop, gizzard, septa, intestine, and dorsal blood vessel
Digestive System
The digestive system consists of the pharynx, the esophagus, the crop, the intestine, and the gizzard. Food enters the earthworms mouth, where the pharynx swallows it. It passes through the esophagus, where the worms calciferous glands will rid the worm of excess calcium. It then moves on the the crop where it might be stored, and if not it moves on into the gizzard. The gizzard grinds the food, and then moves on to the intestines, where it is digested and the digested food is absorbed into the blood vessels. In order to distribute the food to other organs of the body the circulatory system needs to be present, so the minerals are carried away.
Earthworm
Dorsal side of the earthworm
A Lose-Lose
Humans are one of the top predators to worms. They are caught and used for bait and other reasons, but without earthworms the soil be as rich as it would be. Taking the earthworms our is harming us as much as it is harming them. Also global warming is affecting their stable environment causing many earthworms to die. Pollution is also something that is slowly killing them off. Our influence on the earthworms is definitely not a good one, and even though they are helping the environment we are still harming them and killing them.
The Amazing World Of Earthworms In The UK - Springwatch - BBC Two